GEO005 Exam 1 Review - Units 1 and 2

Units 1 and 2

Earth’s 4 major layers

Crust (solid), mantle (solid), outer core (liquid), inner core (solid)

mantle convection, resulting from the original heat of formation of the planet, heat generated by crystallization of the core, and heat supplied by radioactive decay of elements scattered throughout the mantle

moves from higher to lower temperatures through conduction, convection, or radiation

The earth’s inner core is hotter than the outer core because it’s under more pressure

is how the earth’s internal heat is acquired

why the interior of the earth is layered

either through physical properties or chemical composition

The internal structure was formed due to the manner it was formed - planetary accretion

why the outer core is liquid, but the hotter inner core is solid?

the outer core is a liquid because it is under less pressure than the inner core, allowing the molten iron and nickel to remain in a liquid state.

It is the only layer that remains hotter than its melting point temp.

strong outer shell of the Earth consisting of the crust and uppermost (coldest, strongest) layer of the mantle is called the…

• Can break but does not readily flow

• The breaking of it into separate “plates” is what gave rise to the term “plate tectonics”

lithosphere

Weakest layer of the mantle (flows readily) and underlies the ______

• it’s weakness allows tectonic plates to slide around the surface of the Earth

• Though it can flow like a fluid, it is a solid (like the rest of the mantle, similar to silly putty)

is called asthenosphere.

What evidence did Alfred Wegener use to suggest the existence of continental drift

evidence from continents (continents fitting together like a puzzle), evidence for Paleoclimate (such as glacial deposits at the equator, fossil tropical plants found in the Arctic Ocean and coral reefs found in Antartica), evidence from rocks and structural similarities (as well as geological formations across continents showing similar ages and compositions, such as matching mountain ranges on different continents [e.g. Atlas and Appalachian Mountains] and identical volcanic flows of both sides of the Atlantic), and evidence from fossils (fossils from non-swimmer species found on now-separated continents, indicating they were once connected)

volcanic rocks being magnetized in directions opposite of Earth’s magnetic field suggested…

The needle point of a compass pointing south would indicate what…

How we know that our magnetic field has reversed itself many times

magnetic lineations on the seafloor that reveal how ocean crust is created and then moves away from “spreading centers” (also called…)

tectonic plates moving away or diverging from one another is a…

mid-ocean ridges

what is it called when two tectonic plates (such as an oceanic and continental) meet and collide with another one, where the denser one is forced under the less dense tectonic plate

subduction zone

what is it called when two plates slide past each other (similar to the San Andreas fault)

transform plate boundary

what is it called when a boundary between continental crust and oceanic crust is not a plate boundary

Passive Plate Margin

what is it called when one continent with most or all of the land mass, also called Pangaea

supercontinent

A continental collision between the Indian Plate and Eurasian Plate, resulting in tectonic plate thickening & uplift creating a mountain formation, caused what?

The high topography of the Himalayas and Tibet

What describes how continents break up and then rejoin…

Steps to rejoining of continents:

1. A continent rifts when it breaks ip

2. As spreading continues an ocean opens, passive margin colls and sediments accumulate

3. Convergence begins; an oceanic plate subducts, creating a volcanic chain at an active margin

4. Terrain accretion-from the sedimentary wedge welds material to the continent

5. As two continents collide orogeny thickens the crust and building

6. The continent erodes, thinning the crust

The Wilson Cycle

Can convection occur within a crystalline solid

Yes, since Earth’s mantle is solid (has a crystalline structure) but deforms like a fluid on short timescales, thus transferring heat through convection, called solid-state convection

Mantle convection drives what?

Plate tectonics

Earth’s liquid iron outer core provides all the elements necessary to generate a ______ using…

• The electrical current which comes from the motion of the electrical conducting liquid iron as the outer core convects

• Convection in the outer core combined with the spin of the planet drives the liquid iron into elongated spirals that act as coils

• Those coils spiral around more liquid iron, this greatly increasing the strength of the magnetic field

Generating a _____ in this manner is called a dynamo

Earth’s magnetic field

What would cause these effects to happen?

Such as:

• Our electrical grid having major problems

  • More charged particles would reach the Earth causing widespread power outages and broken satellites

• Compasses going crazy

• The Auroras perhaps being visible every night everywhere

• Migratory animals who use _____ may face difficulties

• There would be no mass extinctions

Consequences to losing Earth’s magnetic field

What is the largest earthquakes to have occurred in the past 100 years?

Chile (1960), Alaska (1964), Japan (2011), and Kamchatka (1952)

Crust bending like rubber (to store energy), then unbending (releasing energy) is the behavior for…

elastic rebound (subduction zone quakes)

Faults remaining stuck while energy builds, then suddenly slipping when energy is released is behavior for what?

Stick-slip behavior (subduction zone quakes)

Rough spots along the fault that prevent the fault from sliding until they are broken is called…

asperity

How do plates deform before compared to during a subduction zone earthquake?

Before a subduction zone earthquake: the Pacific Plate subduction was pushing Japan towards the west, compressing it (indicated by GPS measurements)

During a subduction zone earthquake: Japan rebounded and moved eastward, releasing stored energy

What occurs in compressional settings like subduction zones…

• The faults is at an angle so that slip along the fault enables the region to shorten

  • Headwall moves up, while footwall moves down

• Fault does not open up

Thrust fault settings

What occurs in extensional settings like subduction zones…

• The fault is at an angle so that slip along the fault enables the region to lengthen

  • Headwall moves down, footwall moves up

• The fault does not open up

Normal fault settings

What occurs in settings where plates slide laterally past each other (left or right)

• The fault is vertical (no headwall or footwall)

• The crust neither lengthens nor shortens

• The fault does not open up

Strike-slip (transform) fault settings

How do movies generally and incorrectly depict earthquakes?

Showing faults opening up

• Faults never open up, instead the two sides always slide past each other

What type of wave has this properties/behaviors?

• A body wave that travels through the earth

• Push-pull motions (compresses and expands like a sound wave)

• Travels through solids, liquids, and gases

• Fastest seismic waves (first to arrive)

P-waves (P for primary or pressure)

What type of wave has this properties/behaviors?

• A body wave that travels through the earth

• Up-down OR side-to-side motion (shearing)

• Will not travel through liquids, only solids

• A slower wave (second to arrive)

S-wave (S for secondary or shear)

What type of wave has this properties/behaviors?

• Travels along the the surface of the Earth

• Side-to-side motion

  • Non-moving base

• Are one of the last waves to arrive, BUT cause the most shaking

  • Waves die out with depth with wave propagation

Love waves

What type of wave has this properties/behaviors?

• Travels along the surface of a solid or liquid

• Up-down (rolling) motion similar to an ocean wave

  • Has a non-moving base

• Are also one of the last waves to arrive, but cause the most deformation

Rayleigh waves

How many seismograms are required to locate an earthquake?

3

How do we know Earth’s outer core is liquid and the inner core is solid?

Beno Gutenburg discovered the Earth’s outer core was liquid from S-wave shadow zones (1913)

• Seismic waves will curve while propagating

Danish seismologist, Inge Lehmann discovered Earth’s solid inner core (1936) from deflections of P-waves at the inner core/outer core boundary

How are earthquake magnitudes related to the relative magnitude of shaking?

Is on a logarithmic scale: For every whole number increase in magnitude, the amplitude of shaking increases by a factor of 10.

What is the theoretical maximum earthquake magnitude?

10

What is the influence of loose sediments on earthquake shaking?

Loose sediments amplify seismic shaking, similar to Jell-O being shaken.

• Sediments in a basin can greatly increase/magnify the amplitude and duration of shaking

What is used to describe the shaking people and buildings actually feel during earthquakes?

• Is influenced by an earthquakes magnitude, distance from earthquake, and local geology (like sediments)

Mercalli Intensity Scale

Why are earthquakes felt further away in the Eastern U.S. compared to the Western U.S.?

Shaking is more intense in the east because the crust is stronger and less fractured (less active faults breaking it up) and better transmits seismic waves